CN112327347A

CN112327347A - Digital nuclear pulse forming system with adjustable curvature

Info

Publication number: CN112327347A
Application number: CN202011179265.4A
Authority: CN
Inventors: 胡锐; 肖明
Original assignee: Cgn Jiuyuan Chengdu Technology Co ltd
Current assignee: Cgn Jiuyuan Chengdu Technology Co ltd
Priority date: 2020-10-29
Filing date: 2020-10-29
Publication date: 2021-02-05
Anticipated expiration: 2040-10-29
Also published as: CN112327347B

Abstract

The invention provides a curvature-adjustable digital nuclear pulse forming system, which utilizes a digital radiation detector signal as an input signal and outputs a forming signal with adjustable rising edge curvature through cascade operations of an analog response eliminator, a form-adjustable top-hat filter, a two-stage accumulator, amplitude normalization and the like. The common and important nuclear pulse forming signals such as triangle, trapezoid, Gaussian, apex and the like can be formed by adjusting the curvature of the rising edge of the output signal. The method samples the FPGA to realize the system, all the operations adopt a digital processing mode, and the method has the characteristics of simple method, simple system realization, low cost, adjustable various forming pulses and the like.

Description

Digital nuclear pulse forming system with adjustable curvature

Technical Field

The invention belongs to the field of nuclear instrument and nuclear radiation detection, and particularly relates to a curvature-adjustable digital nuclear pulse forming system.

Background

In the field of nuclear instrument instruments and nuclear radiation detection, a nuclear pulse forming system can carry out filter forming on input nuclear signals, so that the signal-to-noise ratio of the system is improved, and subsequent nuclear pulse amplitude measurement and count rate measurement are facilitated. In nuclear electronics, in addition to requiring a certain shape of the signal from the viewpoint of improving the signal-to-noise ratio, there are also other requirements on the signal waveform. For example, at high count rates, it is desirable to shape the waveform narrower to reduce signal overlap; in amplitude analysis it is desirable to have a flat top at the top of the shaped waveform to facilitate accurate amplitude measurement, and in time analysis it is desirable to have steeper edges of the signal to allow accurate timing.

The common analog or digital nuclear pulse forming method and system can only realize the output of one or two waveforms, and are difficult to output forming signals of different waveforms through flexible configuration so as to meet different forming requirements.

According to the forming method and the forming system, common and important nuclear pulse forming signals such as triangles, trapezoids, gaussians, apexes and the like can be formed by adjusting the curvature of the rising edge of the output signal. The method samples the FPGA to realize the system, all the operations adopt a digital processing mode, and the method has the characteristics of simple method, simple system realization, low cost, adjustable various forming pulses and the like.

Disclosure of Invention

The invention aims to provide a digital nuclear pulse forming system with adjustable curvature, aiming at the defects of the prior art, and the digital nuclear pulse forming system with adjustable curvature can well solve the problems.

In order to meet the requirements, the technical scheme adopted by the invention is as follows: the digital nuclear pulse forming system with the adjustable curvature comprises the following components:

using FPGA as a core device for algorithm realization;

a system for realizing the curvature-adjustable digital nuclear pulse forming method is built by combining and cascading units such as an analog response eliminator, a top hat filter, an accumulator, amplitude normalization and the like;

the analog response eliminator is used for deconvolving an input signal from the detector into an impulse response signal;

the top hat filter is used for processing the impact response signal into an inverted top hat signal;

the accumulator is used for integrating signals;

the amplitude normalization unit is used for recovering the amplitude increase caused by multiple integration.

The digital nuclear pulse forming system with the adjustable curvature has the following beneficial effects:

(1) the curvature of the rising and falling edges of the parameter control signal t [ n ] can be adjusted. Varying the curvature can achieve different shaping shapes, such as triangle, trapezoid, gaussian, apex, etc. common and important nuclear pulse shaping signals.

(2) The flat top width of the signal t [ n ] can be controlled to obtain ballistic deficit immunity.

(3) The whole process is automatically and continuously carried out, the algorithm is realized in the FPGA, and the method has simpler realization logic. The requirement on hardware circuits is low.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 schematically shows a system diagram according to an embodiment of the present application.

Fig. 2 schematically shows a schematic diagram of constructing differently shaped signals according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail with reference to specific embodiments below.

In the following description, references to "one embodiment," "an embodiment," "one example," "an example," etc., indicate that the embodiment or example so described may include a particular feature, structure, characteristic, property, element, or limitation, but every embodiment or example does not necessarily include the particular feature, structure, characteristic, property, element, or limitation. Moreover, repeated use of the phrase "in accordance with an embodiment of the present application" although it may possibly refer to the same embodiment, does not necessarily refer to the same embodiment.

Certain features that are well known to those skilled in the art have been omitted from the following description for the sake of simplicity.

According to an embodiment of the application, a curvature-adjustable digital nuclear pulse forming system is provided, the system uses an FPGA as a core device realized by an algorithm, and a system capable of realizing the curvature-adjustable digital nuclear pulse forming method is built by combining and cascading units such as an analog response eliminator, a top-hat filter, an accumulator, amplitude normalization and the like;

(1) the analog response eliminator can deconvolve an input signal from the detector into an impulse response signal;

(2) the top hat filter can process the shock response signal into an inverted top hat signal;

(3) the accumulator is used for integrating the signal;

(4) the amplitude normalization unit can recover the amplitude increase due to multiple integration.

The top hat filter is realized by adopting the following steps:

(1) first, a rectangular filter is constructed to obtain two rectangular pulses p [ n ] and q [ n ]. p [ n ] is used for constructing the brim of the top hat filter, q [ n ] is used for constructing the top of the top hat filter;

(2) the signals p [ n ] and q [ n ] adopt the operations of signal delay, amplitude control, addition and subtraction and the like to synthesize a top hat filter;

a top hat filter having the following features:

(1) the impulse response delta n can be shaped into a reverse top-hat wave form r n (the hat brim is positive and the hat top is negative) through the top-hat filter;

(2) the top-hat filter contains gain control, so that the integral area of the filter can be zero, and the baseline drift is prevented during the subsequent accumulation operation;

(3) the top hat filter is internally provided with a time delay link which can control the widths of the hat brim and the hat top.

The signal r [ n ] is integrated by an accumulator to obtain a bipolar and centrosymmetric signal s [ n ]. And integrating the signal s [ n ] by using an accumulator to obtain a target forming waveform t [ n ], wherein the waveform is unipolar and centrosymmetric.

As shown in FIG. 1, the detector input signal x [ n ] (for ease of description, the input signal is assumed to have an amplitude of 1), which is typically a bi-exponential, step signal. According to the document V.T. Jordanov, Nucl. Instrum. Methods Phys. Res. A, 805:63-71 (2016), the impulse response signal δ [ n ] can be obtained by subjecting the signal x [ n ] to an analog response canceller (unsholding).

The signal δ [ n ] may be passed through a top-hat filter (Tophat filter) to form a top-hat waveform. The specific construction process of the top hat filter (Tophat filter) is as follows:

firstly, a rectangular filter is constructed to obtain two rectangular pulses p [ n ] and q [ n ], and recursive equations are shown in formulas (2) and (3) respectively.

p[n] = ∑(δ[n] −δ[n − k]) （1）

q[n] = ∑(δ[n] −δ[n − l]) （2）

The parameters k, l are the width of the rectangle.

p [ n ] is used to construct the brim of the top hat filter and q [ n ] is used to construct the top of the top hat filter. The signals p [ n ] and q [ n ] adopt the operations of signal delay, amplitude control, addition and subtraction, etc. to synthesize a top-hat filter (Tophat filter). The purpose of the gain control is to make the area of the synthesized top-hat filter zero, preventing the baseline drift from occurring during subsequent accumulation operations. The top hat filter inputs the signal r [ n ].

r[n] = l ∙ p[n] + l ∙ p[n − j − l] − k ∙ q[n − k] − k ∙ q[n − j] （3）

j = k + l + m （4）

The parameter m is used to control the flat top width of the shaped signal.

The signal r [ n ] is integrated by accumulator to obtain signal sn, and then integrated by first-stage accumulator to obtain signal t [ n ]. The expressions for the signals s [ n ] and t [ n ] are shown in equations (5) and (6).

s[n] = ∑r[n] = s[n − 1] + r[n] （5）

t[n] = ∑s[n] = t[n − 1] + s[n] （6）

Because the signal t [ n ] has undergone multiple accumulation operations and amplitude amplification, amplitude normalization operation is required to obtain the target signal y [ n ]. The signal y n is the final shaped signal. The signal y [ n ] is left-right symmetric, the forming time is the sum of parameters k and l, and the flat top width is m. The curvature of the rising edge and the falling edge of the signal y [ n ] can be controlled by adjusting the parameters k and l, and signals with different waveforms are constructed.

The frame shown in fig. 1 can be used to realize the digital nuclear pulse shaping with adjustable curvature, and fig. 2 is used to construct shaping signals with different shapes by controlling parameters k, l and m. Common and important nuclear pulse forming signals such as triangles, trapezoids, gaussians, apexes and the like can be constructed based on the method and the system.

The above-mentioned embodiments only show some embodiments of the present invention, and the description thereof is more specific and detailed, but should not be construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the claims.

Claims

1. A curvature-adjustable digital nuclear pulse forming system is characterized by comprising the following components:

using FPGA as a core device for algorithm realization;

the accumulator is used for integrating signals;

2. The curvature-adjustable digital nuclear pulse shaping system of claim 1, wherein: the top hat filter comprises the following implementation steps:

s1: constructing a rectangular filter to obtain two rectangular pulses p [ n ] and q [ n ], wherein p [ n ] is used for constructing the brim of the top hat filter, and q [ n ] is used for constructing the top of the top hat filter;

s2: the signals p [ n ] and q [ n ] adopt the operations of signal delay, amplitude control, addition and subtraction, etc. to synthesize the top-hat filter.

3. The curvature-adjustable digital nuclear pulse shaping system of claim 2, wherein: the impulse response δ n can be shaped into a reversed top-hat waveform r n by the top-hat filter, with the brim positive and the top negative.

4. The curvature-adjustable digital nuclear pulse shaping system of claim 2, wherein: the top hat filter contains a gain control to zero the integrated area of the filter to prevent baseline wander during subsequent accumulation operations.

5. The curvature-adjustable digital nuclear pulse shaping system of claim 2, wherein: the top hat filter contains a delay link for controlling the width of the brim and the top of the hat.

6. A curvature-adjustable digital nuclear pulse shaping system according to any one of claims 3 to 5, wherein:

integrating the signal r [ n ] by an accumulator to obtain a bipolar and centrosymmetric signal s [ n ];

and integrating the signal s [ n ] by using an accumulator to obtain a target forming waveform t [ n ], wherein the waveform is unipolar and centrosymmetric.

7. The curvature-adjustable digital nuclear pulse shaping system of claim 6, wherein: the adjustment of the curvature of the rising edge and the falling edge of the parameter control signal t [ n ] can be realized.

8. The curvature-adjustable digital nuclear pulse shaping system of claim 7, wherein: by adjusting the curvature, at least four shaping shapes can be obtained, which comprise a common and important nuclear pulse shaping signal.

9. The curvature-adjustable digital nuclear pulse shaping system of claim 7, wherein: ballistic deficit immunity can be achieved by controlling the plateau width of the signal t [ n ].